United States Attorney-General Janet Reno says that stopping crime on the internet is one of the US Government's top priorities.

Hackers disrupted a number of major US websites for the third day running on Wednesday, threatening to damage the growth of e-commerce.

"We are committed in every way possible to tracking down those who are responsible, to bringing them to justice, and to seeing that the law is enforced," Ms Reno told a news conference at FBI headquarters.

Senate Judiciary Committee Chairman Orrin Hatch said he planned to hold hearings soon into what he termed a threat to the US economy.

"In our new, knowledge-based economy, where the internet and e-commerce dominate, public confidence in the security and integrity of the system is paramount," he said.

And Senate Majority Leader, Trent Lott, said he was considering possible legislation to address possible risks to national security from hackers tampering with government computer systems.



Private help



The latest targets include the online brokerage firm E*Trade and a technology news site ZDNet, which were both hit on Wednesday.

On Monday, the world's most popular website, search engine Yahoo, was hit. On Tuesday, Amazon and eBay suffered cyber attacks.

The FBI is seeking private help in solving what it calls the largest computer attack in memory on the internet.

"We're going to need the help of everyone in the community to resolve this," said Ron Dick, chief of the FBI's computer investigation section.

The attacks could have been launched by a single hacker, but the FBI noted that it was "always a possibility" that a foreign government was responsible.

If traced, hackers could face up to 10 years in jail and a $250,000 fine.

Mr Dick urged the private sector to report any attacks promptly so tracing of computers responsible could begin quickly.

And he urged private internet sites to keep logs of traffic, install any tools developed to thwart such attacks and keep them updated.

"The key to this is prevention," Mr Dick said, "implementing appropriate security measures such that you do not allow your system to be used in some of these attacks."

Websites swamped

US officials described the hacks as a "distributed denial of service" attack on US businesses.

Such an assault swamps a website with so many requests for pages that legitimate users cannot access material, the cyber equivalent of jamming a telephone switchboard by making hundreds of calls simultaneously.

A denial of service attack can be orchestrated by software known as daemons, which a hacker hides on hundreds or even thousands of innocent third-party computers.

The daemons can be triggered later from a remote location to launch simultaneous requests to a single target, such as Yahoo! or E*Trade.

The attacking daemons give false addresses so they are harder to trace.

The volume of attacks overwhelms the target and causes it to cease operation.

Many tools for such an attack exist on Internet Web sites, and anyone can download them, he said.

"They do not take much technical expertise to use," Mr Dick said. "A 15-year-old kid could launch these attacks. This is not something that it takes a great deal of sophistication to do."

Investigators are starting from victim computers and tracking the attacks back through the internet service providers that delivered the attacking daemons.

Mr Dick likened it to tracking a trail left by bank robbers from the bank to their hideout.